Lena Dunham is adding author to her resume. A publishing source tells Page Six the creator and star of the HBO series “Girls” is shopping a book proposal this week that’s set to go for a minimum $1 million. “Instead of just auctioning off the book to the highest bidder and having them publish it, they are doing it in a unique way,” says the insider. “The top five bidders in this week’s auction will sit down with Lena on Friday for a meeting. She’ll then choose from those offers.” Being shopped with the title “Not That Kind of Girl,” the book’s said to be a modern take on “Sex and the Single Girl,” written by the late, legendary Cosmopolitan editor Helen Gurley Brown.